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(Created page with '*back to Slicer FAQ = How many sample points should I choose for my registration = *'''Problem:''' unsure what the ''Sample Points'' setting means or how…')
 
 
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*'''Problem:''' unsure what the ''Sample Points'' setting means or how I could use it to improve my registration.
 
*'''Problem:''' unsure what the ''Sample Points'' setting means or how I could use it to improve my registration.
 
*'''Explanation:'''All registration modules contain a parameter field that controls how much of the image is sampled when performing an automated registration. The unit is often an absolute count, but in some cases also a percentage. Default settings also vary among modules. The number of samples is an important setting that determines both registration speed and quality. If the sample number is too small, registration may fail because it is driven by image content that insufficiently represents the image. If sample number is too large, registration can slow down significantly.
 
*'''Explanation:'''All registration modules contain a parameter field that controls how much of the image is sampled when performing an automated registration. The unit is often an absolute count, but in some cases also a percentage. Default settings also vary among modules. The number of samples is an important setting that determines both registration speed and quality. If the sample number is too small, registration may fail because it is driven by image content that insufficiently represents the image. If sample number is too large, registration can slow down significantly.
−
*'''Fix:''' If registration speed is not a major issue, better to err on the side of larger samples. Most default settings are chosen to yield relatively fast registrations and for most of today's image represent only a small percentage. The table below relates total sample points and percentages to the most common image sizes. Also consider that sample points are chosen randomly so that some points may fall outside the actual object to be registered. That is not a bad thing per se, some background points are important, but not if they are too far from the edges of the object.
+
*'''Fix:''' If registration speed is not a major issue, better to err on the side of larger samples. Most default settings are chosen to yield relatively fast registrations and for most of today's image represent only a small percentage. Below the defaults for the different registration modules, for version 3.6.1:
 +
  '''Defaults Used in Slicer Modules v.3.6.1'''
 
   Fast Rigid / Linear: 10,000
 
   Fast Rigid / Linear: 10,000
 
   Fast Affine: 10,000
 
   Fast Affine: 10,000
Line 16: Line 17:
 
   Robust Multiresolution: N/A
 
   Robust Multiresolution: N/A
 
   Surface Registration: 200
 
   Surface Registration: 200
 +
 +
The table below relates total sample points and percentages to the most common image sizes. Also consider that sample points are chosen randomly so that some points may fall outside the actual object to be registered. That is not a bad thing per se, some background points are important, but not if they are too far from the edges of the object. So consider both total image size as well as the percentage of the image field of view that your object of interest obtains. E.g. if your object fills only half the image, double the sample points to get the desired amount of points within the object.
 +
 +
{| class="wikitable sortable labelpage labelpagetable" border="1"
 +
|-
 +
! Image Size
 +
! Total Points
 +
! 10,000
 +
! 50,000
 +
! 100,000
 +
! 200,000
 +
! 1%
 +
! 2%
 +
! 5%
 +
! 10%
 +
! 20%
 +
|-
 +
| 128 x 128 x 64
 +
|1048576
 +
|1.0%
 +
|4.8%
 +
|9.5%
 +
|19.1%
 +
|~10000
 +
|~20000
 +
|~52500
 +
|~100000
 +
|~200000
 +
|-
 +
|-
 +
| 256 x 256 x 30
 +
|1966080
 +
|0.5%
 +
|2.5%
 +
|5.1%
 +
|10.2%
 +
|~20000
 +
|~40000
 +
|~97500
 +
|~200000
 +
|~400000
 +
|-
 +
|-
 +
| 256 x 256 x 120
 +
|7864320
 +
|0.1%
 +
|0.6%
 +
|1.3%
 +
|2.5%
 +
|~77500
 +
|~150000
 +
|~400000
 +
|~775000
 +
|~1500000
 +
|-
 +
|-
 +
| 192 x 192 x 192
 +
|7077888
 +
|0.1%
 +
|0.7%
 +
|1.4%
 +
|2.8%
 +
|~70000
 +
|~150000
 +
|~350000
 +
|~700000
 +
|~1500000
 +
|-
 +
|-
 +
| 512 x 512 x 48
 +
|12582912
 +
|0.1%
 +
|0.4%
 +
|0.8%
 +
|1.6%
 +
|~125000
 +
|~250000
 +
|~625000
 +
|~1250000
 +
|~2500000
 +
|-
 +
|-
 +
| 256 x 256 x 256
 +
|16777216
 +
|0.1%
 +
|0.3%
 +
|0.6%
 +
|1.2%
 +
|~175000
 +
|~325000
 +
|~850000
 +
|~1750000
 +
|~3250000
 +
|-
 +
|-
 +
| 512 x 512 x 160
 +
|41943040
 +
|0.0%
 +
|0.1%
 +
|0.2%
 +
|0.5%
 +
|~425000
 +
|~850000
 +
|~2000000
 +
|~4250000
 +
|~8500000
 +
|}

Latest revision as of 15:25, 16 November 2010

Home < Projects:SlicerFAQ:SamplePoints

How many sample points should I choose for my registration

  • Problem: unsure what the Sample Points setting means or how I could use it to improve my registration.
  • Explanation:All registration modules contain a parameter field that controls how much of the image is sampled when performing an automated registration. The unit is often an absolute count, but in some cases also a percentage. Default settings also vary among modules. The number of samples is an important setting that determines both registration speed and quality. If the sample number is too small, registration may fail because it is driven by image content that insufficiently represents the image. If sample number is too large, registration can slow down significantly.
  • Fix: If registration speed is not a major issue, better to err on the side of larger samples. Most default settings are chosen to yield relatively fast registrations and for most of today's image represent only a small percentage. Below the defaults for the different registration modules, for version 3.6.1:
 Defaults Used in Slicer Modules v.3.6.1
 Fast Rigid / Linear: 10,000
 Fast Affine: 10,000
 Fast Rigid: 10,000
 Fast Non-Rigid BSpline: 50,000
 Expert Automated (Rigid): 1%
 Expert Automated (Affine): 2%
 Expert Automated (BSpline): 10%
 BRAINSfit: 100,000
 BRAINSdemon Warp: N/A 
 Robust Multiresolution: N/A
 Surface Registration: 200

The table below relates total sample points and percentages to the most common image sizes. Also consider that sample points are chosen randomly so that some points may fall outside the actual object to be registered. That is not a bad thing per se, some background points are important, but not if they are too far from the edges of the object. So consider both total image size as well as the percentage of the image field of view that your object of interest obtains. E.g. if your object fills only half the image, double the sample points to get the desired amount of points within the object.

Image Size Total Points 10,000 50,000 100,000 200,000 1% 2% 5% 10% 20%
128 x 128 x 64 1048576 1.0% 4.8% 9.5% 19.1% ~10000 ~20000 ~52500 ~100000 ~200000
256 x 256 x 30 1966080 0.5% 2.5% 5.1% 10.2% ~20000 ~40000 ~97500 ~200000 ~400000
256 x 256 x 120 7864320 0.1% 0.6% 1.3% 2.5% ~77500 ~150000 ~400000 ~775000 ~1500000
192 x 192 x 192 7077888 0.1% 0.7% 1.4% 2.8% ~70000 ~150000 ~350000 ~700000 ~1500000
512 x 512 x 48 12582912 0.1% 0.4% 0.8% 1.6% ~125000 ~250000 ~625000 ~1250000 ~2500000
256 x 256 x 256 16777216 0.1% 0.3% 0.6% 1.2% ~175000 ~325000 ~850000 ~1750000 ~3250000
512 x 512 x 160 41943040 0.0% 0.1% 0.2% 0.5% ~425000 ~850000 ~2000000 ~4250000 ~8500000
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